Molecules, such as vitamins, fatty acids, essential oils, are very widely used in many technical fields such as the pharmaceutical, cosmetic and agri-food industries, and in particular in the animal nutrition field. As an example, vitamins A and E are commonly used for the preparation of feed promoting animal growth and health.
Their hydrophobic nature and their environmental, in particular thermal and chemical fragility, during their formulation and storage, as well as during their use, make their encapsulation necessary.
The vitamin E, or tocopherol (in abbreviated form, TOL), existing predominantly in the form of α-tocopherol (αTOL), is, in the native state, an oily, lipophilic, miscible liquid in all proportions in any hydrophobic or lipid phase. It is extremely unstable, easily oxidizable and, in the oxidized state, it loses most of its biological activity. Its bioavailability in animals does not exceed 50% when it is orally administered, since, rapidly oxidized, it is mainly absorbed in this oxidized, inactive form. Also, when it is orally administered, vitamin E is in the form of a more stable derivative, generally selected from esters, for example acetate, and vitamin E salts.
The vitamin A exists in several forms, in particular as an ester, and it is in one of its most stable forms, the retinyl acetate form, that it is most often consumed by livestock animals (poultry, pigs and cattle). However, it remains sensitive to oxidation, temperature, light, acids. In pharmaceutical application or animal nutrition, it is thus very rapidly degraded as soon as it meets the first severe conditions, in particular acidic conditions, of the digestive system, which does not make it a bioavailable form of the vitamin A.
In order to best preserve these sensitive active ingredients, it is known for long that they can be protected by coating or encapsulation. Various means for encapsulating vitamins in particular A and E have been developed and widely used, such as means involving proteins.